The 1955 Air Pollution Control Act was the first U.S federal legislation that pertained to air pollution; it also provided funds for federal government research of air pollution.[4] The first federal legislation to actually pertain to "controlling" air pollution was the Clean Air Act of 1963.[5] The 1963 act accomplished this by establishing a federal program within the U.S. Public Health Service and authorizing research into techniques for monitoring and controlling air pollution.[6]

It was first amended in 1965, by the Motor Vehicle Air Pollution Control Act, which authorized the federal government to set required standards for controlling the emission of pollutants from certain automobiles, beginning with the 1968 models. A second amendment, the Air Quality Act of 1967, enabled the federal government to increase its activities to investigate enforcing interstate air pollution transport, and, for the first time, to perform far-reaching ambient monitoring studies and stationary source inspections. The 1967 act also authorized expanded studies of air pollutant emission inventories, ambient monitoring techniques, and control techniques.[7]

Amendments approved in 1970 greatly expanded the federal mandate, requiring comprehensive federal and state regulations for both stationary (industrial) pollution sources and mobile sources. It also significantly expanded federal enforcement. Also, EPA was established on December 2, 1970 for the purpose of consolidating pertinent federal research, monitoring, standard-setting and enforcement activities into one agency that ensures environmental protection.[8]

Further amendments were made in 1990 to address the problems of acid rain, ozone depletion, and toxic air pollution, and to establish a national permit program for stationary sources, and increased enforcement authority. The amendments also established new auto gasoline reformulation requirements, set Reid vapor pressure (RVP) standards to control evaporative emissions from gasoline, and mandated new gasoline formulations sold from May to September in many states.

The Clean Air Act was the first major environmental law in the United States to include a provision for citizen suits. Numerous state and local governments have enacted similar legislation, either implementing federal programs or filling in locally important gaps in federal programs.

This section of the act declares that protecting and enhancing the nation's air quality promotes public health. The law encourages prevention of regional air pollution and control programs. It also provides technical and financial assistance for air pollution prevention at both state and local governments. Additional subchapters cover of cooperation, research, investigation, training and other activities. Grants for air pollution planning and control programs, and interstate air quality agencies and program cost limitations are also included in this section of the act.[10]

The act mandates air quality control regions, designated as attainment vs non-attainment. Non-attainment areas do not meet national standards for primary or secondary ambient air quality. Attainment areas meet these standards, while unclassifiable areas cannot be classified on the basis of the information that is available.[10]

Air quality criteria, national primary and secondary ambient air quality standards, state implementation plans and performance standards for new stationary sources are also covered in Part A. The list of hazardous air pollutants established by the act includes acetaldehyde, benzene, chloroform, phenols and selenium compounds. The list also includes mineral fiber emissions from manufacturing or processing glass, rock or slag fibers as well as radioactive atoms. The list periodically can be modified. The act lists unregulated radioactive pollutants such as cadmium, arsenic, and polycyclic organic matter and mandates listing them if they will cause or contribute to air pollution that endangers public health, under section 7408 or 7412.[10]

The remaining subchapters cover smokestack heights, state plan adequacy, and estimating emissions of carbon monoxide, volatile organic compounds, and oxides of nitrogen from area and mobile sources. Measures to prevent unemployment or other economic disruption include using local coal or coal derivatives to comply with implementation requirements. The final subchapter in this act focuses on land use authority.[10]

Because of advances in the atmospheric chemistry, this section was replaced by Title VI when the law was amended in 1990.[11]

This change in the law reflected significant changes in scientific understanding of ozone formation and depletion. Ozone absorbs UVC light and shorter wave UVB, and lets through UVA, which is largely harmless to people. Ozone exists naturally in the stratosphere, not the troposphere. It is laterally distributed because it is destroyed by strong sunlight, so there is more ozone at the poles. Ozone is created when O2 comes in contact with photons from solar radiation. Therefore, a decrease in the intensity of solar radiation also results in a decrease in the formation of ozone in the stratosphere. This exchange is known as the Chapman mechanism:

M represents a third molecule, needed to carry off the excess energy of the collision of O + O2.

Atmospheric freon and chlorofluorocarbons (CFCs) contribute to ozone depletion (Chlorine is a catalytic agent in ozone destruction). Following discovery of the ozone hole in 1985, the 1987 Montreal Protocol successfully implemented a plan to replace CFCs and was viewed by some environmentalists as an example of what is possible for the future of environmental issues, if the political will is present.

The Clean Air Act requires permits to build or add to major stationary sources of air pollution. This permitting process, known as New Source Review (NSR), applies to sources in areas that meet air quality standards as well as areas that are unclassifiable.[12] Permits in attainment or unclassifiable areas are referred to as Prevention of Significant Deterioration (PSD) permits, while permits for sources located in nonattainment areas are referred to as nonattainment area (NAA) permits.[13]

Under the Clean Air Act states are required to submit a plan for non-attainment areas to reach attainment status as soon as possible but in no more than five years, based on the severity of the air pollution and the difficulty posed by obtaining cleaner air.

The plan must include:

an inventory of all pollutants

permits

control measures, means and techniques to reach standard qualifications

contingency measures

The plan must be approved or revised if required for approval, and specify whether local governments or the state will implement and enforce the various changes. Achieving attainment status makes a request for reevaluation possible. It must include a plan for maintenance of air quality.

Subchapters of Title II cover state standards and grants, prohibited acts and actions to restrain violations, as well as a study of emissions from nonroad vehicles (other than locomotives) to determine whether they cause or contribute to air pollution. Motorcycles are treated in the same way as automobiles under the emission standards for new motor vehicles or motor vehicle engines. The last few subchapters deal with high altitude performance adjustments, motor vehicle compliance program fees, prohibition on production of engines requiring leaded gasoline and urban bus standards.[14]

This part of the bill was extremely controversial the time it was passed. The automobile industry argued that it could not meet the new standards. Senators expressed concern about impact on the economy. Specific new emissions standards for moving sources passed years later.

Trucks and automobiles play a large role in deleterious air quality. Harmful chemicals such as nitrogen oxide, hydrocarbons, carbon monoxide and sulfur dioxide are released from motor vehicles. Some of these also react with sunlight to produce photochemicals.[18] These harmful substances change the climate, alter ocean pH and include toxins that may cause cancer, birth defects or respiratory illness. Motor vehicles increased in the 1990s since approximately 58 percent of households owned two or more vehicles.[18] The Clean Fuel Vehicle programs focused on alternative fuel use and petroleum fuels that met low emission vehicle (LEV) levels. Compressed natural gas, ethanol,[19]methanol,[20] liquefied petroleum gas and electricity are examples of cleaner alternative fuel. Programs such as the California Clean Fuels Program and pilot program are increasing demand that for new fuels to be developed to reduce harmful emissions.[18]

The California pilot program incorporated under this section focuses on pollution control in ozone non-attainment areas. The provisions apply to light-duty trucks and light-duty vehicles in California. The state also requires that clean alternative fuels for sale at numerous locations with sufficient geographic distribution for convenience. Production of clean-fuel vehicles isn't mandated except as part of the California pilot program.[10]

Under the law prior to 1990, EPA was required to construct a list of Hazardous Air Pollutants as well as health-based standards for each one. There were 187 air pollutants listed and the source from which they came. The EPA was given ten years to generate technology-based emission standards. Title III is considered a second phase, allowing the EPA to assess lingering risks after the enactment of the first phase of emission standards. Title III also enacts new standards with regard to the protection of public health.[21]

A citizen may file a lawsuit to obtain compliance with an emission standard issued by the EPA or by a state, unless there is an ongoing enforcement action being pursued by EPA or the appropriate state agency.[22]

This title pre-dates the Clean Air Act. With the passage of the Clean Air Act, it became codified as Title IV. However, another Title IV was enacted in the 1990 amendments. The second Title IV was then appended to this Title IV as Title IV-A (see below).

This title established the EPA Office of Noise Abatement and Control to reduce noise pollution in urban areas, to minimize noise-related impacts on psychological and physiological effects on humans, effects on wildlife and property (including values), and other noise-related issues. The agency was also assigned to run experiments to study the effects of noise.

This title was added as part of the 1990 amendments. It addresses the issue of acid rain, which is caused by nitrogen oxides (NOX) and sulfur dioxide (SO2) emissions from electric power plants powered by fossil fuels, and other industrial sources. The 1990 amendments gave industries more pollution control options including switching to low-sulfur coal and/or adding devices that controlled the harmful emissions. In some cases plants had to be closed down to prevent the dangerous chemicals from entering the atmosphere.[23]

Title IV-A mandated a two-step process to reduce SO2 emissions. The first stage required more than 100 electric generating facilities larger than 100 megawatts to meet a 3.5 million ton SO2 emission reduction by January 1995. The second stage gave facilities larger than 75 megawatts a January 2000 deadline.[23]

The 1990 amendments authorized a national operating permit program, covering thousands of large industrial and commercial sources.[24] It required large businesses to address pollutants released into the air, measure their quantity, and have a plan to control and minimize them as well as to periodically report. This consolidated requirements for a facility into a single document.[24]

In non-attainment areas, permits were required for sources that emit as little as 50, 25, or 10 tons per year of VOCs depending on the severity of the region’s non-attainment status.[25]

Most permits are issued by state and local agencies.[26] If the state does not adequately monitor requirements, the EPA may take control. The public may request to view the permits by contacting the EPA. The permit is limited to no more than five years and requires a renewal.[25]

Starting in 1990, Title VI mandated regulations regarding the use and production of chemicals that harm the Earth’s stratospheric ozone layer. This ozone layer protects against harmful ultraviolet B sunlight linked to several medical conditions including cataracts and skin cancer.[27]

The ozone-destroying chemicals were classified into two groups, Class I and Class II. Class I consists of substances, including chlorofluorocarbons, that have an ozone depletion potential (ODP) (HL) of 0.2 or higher. Class II lists substances, including hydrochlorofluorocarbons, that are known to or may be detrimental to the stratosphere. Both groups have a timeline for phase-out:

For Class I substances, no more than seven years after being added to the list and

Title VI establishes methods for preventing harmful chemicals from entering the stratosphere in the first place, including recycling or proper disposal of chemicals and finding substitutes that cause less or no damage.[28] The Significant New Alternatives Policy (SNAP) Program is EPA's program to evaluate and regulate substitutes for the ozone-depleting chemicals that are being phased out under the stratospheric ozone protection provisions of the Clean Air Act.[29]

Over 190 countries signed the Montreal Protocol in 1987, agreeing to work to eliminate or limit the use of chemicals with ozone-destroying properties.[27]

Congress passed the first legislation to address air pollution with the 1955 Air Pollution Control Act that provided funds to the U.S. Public Health service, but did not formulate pollution regulation.[30] However, the Clean Air Act in 1963, created a research and regulatory program in the U.S. Public Health Service.[31] The Act authorized development of emission standards for stationary sources, but not mobile sources of air pollution.[32]:211 The 1967 Air Quality Act mandated enforcement of interstate air pollution standards and authorized ambient monitoring studies and stationary source inspections.[33]

In the Clean Air Act Extension of 1970, Congress greatly expanded the federal mandate by requiring comprehensive federal and state regulations for both industrial and mobile sources.[34] The law established four new regulatory programs:

The 1970 law is sometimes called the "Muskie Act" because of the central role Maine Senator Edmund Muskie played in drafting the bill.[36]

To implement the strict new Clean Air Act of 1970, during his first term as EPA Administrator William Ruckelshaus spent 60% of his time on the automobile industry, whose emissions were to be reduced 90% under the new law. Senators had been frustrated at the industry’s failure to cut emissions under previous, weaker air laws.[37]

The Clean Air Act Amendments of 1977 required Prevention of Significant Deterioration (PSD) of air quality for areas attaining the NAAQS and added requirements for non-attainment areas.[38]

The 1990 Clean Air Act added regulatory programs for control of acid deposition (acid rain) and stationary source operating permits. The amendments moved considerably beyond the original criteria pollutants, expanding the NESHAP program with a list of 189 hazardous air pollutants to be controlled within hundreds of source categories, according to a specific schedule.[39] The NAAQS program was also expanded. Other new provisions covered stratospheric ozone protection, increased enforcement authority and expanded research programs.[40]

The legal authority for federal programs regarding air pollution control is based on the 1990 Clean Air Act Amendments (1990 CAAA). These are the latest in a series of amendments made to the Clean Air Act (CAA), often referred to as "the Act." This legislation modified and extended federal legal authority provided by the earlier Clean Air Acts of 1963 and 1970.[7]

The 1955 Air Pollution Control Act was the first federal legislation involving air pollution; it authorized $3 million per year to the U.S. Public Health Service for five years to fund federal level air pollution research, air pollution control research, and technical and training assistance to the states. Subsequently, the act was extended for four years in 1959 with funding levels at $5 million per year. The act was then amended in 1960 and 1962. Although the 1955 act brought the air pollution issue to the federal level, no federal regulations were formulated. Control and prevention of air pollution was instead delegated to state and local agencies.[30]

The Clean Air Act of 1963 was the first federal legislation regarding air pollution control. It established a federal program within the U.S. Public Health Service and authorized research into techniques for monitoring and controlling air pollution. In 1967, the Air Quality Act was enacted in order to expand federal government activities. In accordance with this law, enforcement proceedings were initiated in areas subject to interstate air pollution transport. As part of these proceedings, the federal government for the first time conducted extensive ambient monitoring studies and stationary source inspections.

The Air Quality Act of 1967 also authorized expanded studies of air pollutant emission inventories, ambient monitoring techniques, and control techniques.[7]

The Clean Air Act of 1970 (1970 CAA) authorized the development of comprehensive federal and state regulations to limit emissions from both stationary (industrial) sources and mobile sources. Four major regulatory programs affecting stationary sources were initiated:

the National Ambient Air Quality Standards [NAAQS (pronounced "knacks")],

State Implementation Plans (SIPs),

New Source Performance Standards (NSPS),

and National Emission Standards for Hazardous Air Pollutants (NESHAPs).

Enforcement authority was substantially expanded. This very important legislation was adopted at approximately the same time as the National Environmental Policy Act .[7]

Major amendments were added to the Clean Air Act in 1977 (1977 CAAA). The 1977 Amendments primarily concerned provisions for the Prevention of Significant Deterioration (PSD) of air quality in areas attaining the NAAQS. The 1977 CAAA also contained requirements pertaining to sources in non-attainment areas for NAAQS. A non-attainment area is a geographic area that does not meet one or more of the federal air quality standards. Both of these 1977 CAAA established major permit review requirements to ensure attainment and maintenance of the NAAQS.[7]

Another set of major amendments to the Clean Air Act occurred in 1990 (1990 CAAA). The 1990 CAAA substantially increased the authority and responsibility of the federal government. New regulatory programs were authorized for control of acid deposition (acid rain) and for the issuance of stationary source operating permits. The NESHAPs were incorporated into a greatly expanded program for controlling toxic air pollutants. The provisions for attainment and maintenance of NAAQS were substantially modified and expanded. Other revisions included provisions regarding stratospheric ozone protection, increased enforcement authority, and expanded research programs.[7]

This section needs expansion with: additional regulations. You can help by adding to it.(June 2011)

Since the initial establishment of six mandated criteria pollutants (ozone, particulate matter, carbon monoxide, nitrogen oxides, sulfur dioxide, and lead), advancements in testing and monitoring have led to the discovery of many other significant air pollutants.[41]

However, with the act in place and its many improvements, the U.S. has seen many pollutant levels and associated cases of health complications drop. According to the EPA, the 1990 Clean Air Act Amendments has prevented or will prevent:

Year 2010
(cases prevented)

Year 2020
(cases prevented)

Adult Mortality - particles

160,000

230,000

Infant Mortality - particles

230

280

Mortality - ozone

4,300

71,000

Chronic Bronchitis

54,000

75,000

Heart Disease - Acute Myocardial Infarction

130,000

200,000

Asthma Exacerbation

1,700,000

2,400,000

Emergency Room Visits

86,000

120,000

School Loss Days

3,200,000

5,400,000

Lost Work Days

13,000,000

17,000,000

This chart shows the health benefits of the Clean Air Act programs that reduce levels of fine particles and ozone.[42]

The Clean Air Act (CAA or Act) directs EPA to establish national ambient air quality standards (NAAQS) for pollutants at levels that will protect public health. EPA and American Lung Association promoted the 2011 Cross State Air Pollution Rule (CSAPR) to control ozone and fine particles. Aim was to cut emissions half from 2005 to 2014. It was claimed to prevent each year 400,000 asthma cases and save ca 2m work and schooldays lost by respiratory illness. Some states (e.g. Texas), cities and power companies sued the case (EPA v EME Homer City Generation).[47] The appeals-court judges decided by two to one that the rule is too strict. Based on appeals the power companies were allowed to continue thousands of persons respiratory illnesses prolonged time in the USA. According to the Economist (2013) the Supreme Court decision may affect how the EPA regulates other pollutants, including the greenhouse gases.[48]

Although the 1990 Clean Air Act is a federal law covering the entire country, the states do much of the work to carry out the Act. The EPA has allowed the individual states to elect responsibility for compliance with and regulation of the CAA within their own borders in exchange for funding. For example, a state air pollution agency holds a hearing on a permit application by a power or chemical plant or fines a company for violating air pollution limits. However, election is not mandatory and in some cases states have chosen to not accept responsibility for enforcement of the act and force the EPA to assume those duties.

In order to take over compliance with the CAA the states must write and submit a state implementation plan (SIP) to the EPA for approval. A state implementation plan is a collection of the regulations a state will use to clean up polluted areas. The states are obligated to notify the public of these plans, through hearings that offer opportunities to comment, in the development of each state implementation plan. The SIP becomes the state's legal guide for local enforcement of the CAA. For example, Rhode Island law requires compliance with the Federal CAA through the SIP.[49] The SIP delegates permitting and enforcement responsibility to the state Department of Environmental Management (RI-DEM).

The federal law recognizes that states should lead in carrying out the Clean Air Act, because pollution control problems often require special understanding of local industries, geography, housing patterns, etc. However, states are not allowed to have weaker pollution controls than the national minimum criteria set by EPA. EPA must approve each SIP, and if a SIP isn't acceptable, EPA can take over CAA enforcement in that state.

The United States government, through the EPA, assists the states by providing scientific research, expert studies, engineering designs, and money to support clean air programs.

Metropolitan planning organizations must approve all federally funded transportation projects in a given urban area. If the MPO's plans do not, Federal Highway Administration and the Federal Transit Administration have the authority to withhold funds if the plans do not conform with federal requirements, including air quality standards.[50] In 2010, the EPA directly fined the San Joaquin Valley Air Pollution Control District $29 million for failure to meet ozone standards, resulting in fees for county drivers and businesses. This was the results of a federal appeals court case that required the EPA to continue enforce older, stronger standards,[51] and spurred debate in Congress over amending the Act.[52]

Air pollution often travels from its source in one state to another state. In many metropolitan areas, people live in one state and work or shop in another; air pollution from cars and trucks may spread throughout the interstate area. The 1990 Clean Air Act provides for interstate commissions on air pollution control, which are to develop regional strategies for cleaning up air pollution. The 1990 amendments include other provisions to reduce interstate air pollution.

The Act requires industrial facilities to implement a Leak Detection and Repair (LDAR) program to monitor and audit a facility's fugitive emissions of volatile organic compounds (VOC). The program is intended to identify and repair components such as valves, pumps, compressors, flanges, connectors and other components that may be leaking. These components are the main source of the fugitive VOC emissions.

Testing is done manually using a portable vapor analyzer that read in parts per million (ppm). Monitoring frequency, and the leak threshold, is determined by various factors such as the type of component being tested and the chemical running through the line. Moving components such as pumps and agitators are monitored more frequently than non-moving components such as flanges and screwed connectors. The regulations require that when a leak is detected the component be repaired within a set amount of days. Most facilities get 5 days for an initial repair attempt with no more than 15 days for a complete repair. Allowances for delaying the repairs beyond the allowed time are made for some components where repairing the component requires shutting process equipment down.

EPA began regulating greenhouse gases (GHGs) from mobile and stationary sources of air pollution under the Clean Air Act for the first time on January 2, 2011. Standards for mobile sources have been established pursuant to Section 202 of the CAA, and GHGs from stationary sources are controlled under the authority of Part C of Title I of the Act.

Below is a table for the sources of greenhouse gases, taken from data in 2008.[55] Of all greenhouse gases, about 76 percent of the sources are manageable under the CAA, marked with an asterisk (*). All others are regulated independently, if at all.

By promoting pollution reduction, the Clean Air Act can help reduce heightened exposure to air pollution among communities of color and low-income communities.[56] Environmental researcher Dr. Marie Lynn Miranda notes that African American populations are “consistently overrepresented” in areas with the poorest air quality.[57] Dense populations of low-income and minority communities inhabit the most polluted areas across the United States, which is considered to exacerbate health problems among these populations.[58] High levels of exposure to air pollution is linked to several health conditions, including asthma, cancer, premature death, and infant mortality, each of which disproportionately impact communities of color and low-income communities.[59] The pollution reduction achieved by the Clean Air Act is associated with a decline in each of these conditions and can promote environmental justice for communities that are disproportionately impacted by air pollution and diminished health status.[59]

A 2017 study found that the Clean Air Act of 1970 led to an over 10 percent reduction in pollution ("ambient TSP levels") in counties that exceeded the pollution thresholds set by the Act in the three years after the regulation went into effect. The study found that this regulation-induced reduction in air pollution is caused affected workers to work more and earned 1 percent more in annual earnings. The authors estimate that cumulative lifetime income gain for each affected individual is approximately $4,300 in present value terms.[61]

^"The Clean Air Act in a Nutshell: How It Works"(pdf). Retrieved 2014-04-24. Collectively, the PSD permitting program and nonattainment area permitting program for major sources are known as "New Source Review." Before starting the construction of a new major source located in an attainment, or unclassifiable area, or the modification of an existing major source that results in a significant emissions increase in such areas, the source must obtain a PSD permit under the Act.